US 2013/0331929 A1 describes a sealing system that comprises an additional sealing element at the proximal end of a TAVI valve. This contains a hydrogel that is caused to swell by inflowing fluid. The inflow of fluid is allowed only after implantation by a valve that can be controlled from outside.
US 2013/0018458 describes a system consisting of non-swelling materials (here polyethylene terephthalate, PET) that is designed so that in the inflow area of the TAVI valve overhanging materials of the skirt that is normally sutured inside are fixed to the outside of the stent. This is done in such a way that the overhanging material lies loosely in folds against the outside of the stent in the implanted state. This fold formation in the area of the annulus in turn seals existing leakages.
Sealing by swellable hydrogels has negative effects on the durability of these heart valves, since hydrogels generally do not exhibit long-term stability under physiological conditions.
The use of loosely attached PET skirts does not comprise an active element of the seal. Thus, in highly calcified areas of the natural valve annulus leakage flows can still occur, since the PET material cannot conform in a form-fit manner to the calcification.